The operation state of an electric power plant can be monitored by a personal computer (PC) installed in a central operation room. Moreover, the operation of the electric power plant can be operated by providing instructions from the PC in the central operation room to equipment in the electric power plant. However, there have been demands for not fixing the apparatus which monitors and operates the electric power plant to the PC in the central operation room. For example, it is desired to display the operation state of the electric power plant by a PC at the desk of an operator, and to perceive the operation state of the electric power plant while a screen of an operation terminal is checked in a field of the electric power plant.